This invention relates to quadrature detectors and especially to quadrature detectors in which the quadrature components are processed through the identical R.F. circuit components.
Conventional quadrature detection circuitry (see FIG. 1 of the drawing) utilizes two channels of balanced modulation and low-pass filtering to detect the quadrature components (I and Q components) which fully specify the amplitude and phase of an R.F. signal. An input R.F. signal is first power-split and then mixed with two local oscillator (L.O.) signals which are in phase-quadrature with each other. The modulator outputs are then low-pass-filtered to remove the high-frequency sidebands and the carrier-frequency signals. The amplitude and phase of the original R.F. input are specified by the relations: ##EQU1## Since both functions rely on I and Q values, the accuracy of the detection process depends on exact tracking (with respect to input R.F. phase, amplitude and frequency) between the two detection channels. Tracking errors are normally caused by mismatches in the characteristics of the individual R.F. components. These include the balanced modulators, power splitter, and low-pass filter stages. Obviously, to improve the accuracy of the detection process, it is important to reduce or eliminate these mismatches.